Metastasis, which represents the major cause of frustration and failure in therapy, remains the least understood stage of cancer progression. One of the difficulties in studying later stages of metastasis is the lack of appropriate models of the complex metastatic process. To overcome this challenge, we have developed a microfluidic system that recapitulates critical stages of metastasis while allowing for real time stimulation of cell phenotype and real time imaging of the metastatic process. The microfluidic model recapitulates critical aspects of the ectopic site, including a vascular compartment with physiologic flow and functional endothelium and a solid ECM-rich tissue compartment. In this work, we will use this platform to elucidate the importance of HA-dependent mechanisms in tumor cells as drivers of metastasis and ultimately to develop the microfluidic model system as a screening tool for identifying novel anti-metastatic reagents. Our working hypothesis is that HA synthesis and pericellular coat formation by metastatic carcinoma cells confers a `stromal independent' phenotype to enhance metastasis formation. Mechanistically the prediction is that this facilitates survival in the circulation and promotes carcinoma cell adhesion to endothelial cells, subsequent extravasation, and invasion and growth within the parenchyma of tissues harboring metastatic lesions. Within this work, we will specifically: (1) optimize our microfluidic platform to quantify the metastatic potential of breast cancer cells; (2) quantify the effects of altering HA synthesis by metastatic carcinoma cells on tumor cells arrest, extravasation and growth both in vitro and in vivo. While HA synthesis by carcinomas has been linked with malignant progression, we hypothesize that it is the formation of a pericellular rich matrix that positions plasma membrane receptors, organizes the cytoskeleton and functions to maintain survival. Preliminary data support this hypothesis and this will be further tested by limiting HA synthesis and artificially restoring the pericellular matrix, using lipid coupled HA that will intercalate into the plasma membrane. We will evaluate key oncogenic signaling and survival pathways in cells (both suspended and adherent) that have, or do not have, an endogenous or artificial HA rich pericellular matrix. The prediction is that cells with a pericellular HA matrix ill in fact maintain activated oncogenic pathways, independent of adhesion, that will be inhibited by preventing the formation of a pericellular HA rich matrix. Beyond this specific mechanism of metastasis, this model should help focus on critical events in metastasis and ultimately speed the discovery of new therapeutic targets to block rate limiting steps in this process.